Following myocardial infarction (MI), the degradation of cardiac extracellular matrix (ECM) mainly by upregulated matrix metalloproteinase-2/9 (MMP-2/9), and the progression of cardiac fibrosis after myofibroblast formation, progressively deteriorate cardiac function. As such, impeding MMP-2/9 bioactivity, and inhibiting myofibroblast formation will improve cardiac function. However, the ideal therapeutic strategies to simultaneously achieve both goals remain to be established. Currently, systemic delivery of broad spectrum MMP inhibitors did not show consistent outcomes in clinical trials. MMP-2/9 expression is spatiotemporal in infarcted hearts over the course of post-MI. Yet current systemic delivery approach cannot spatiotemporally deliver MMP inhibitors to the infarcted area. To attenuate cardiac fibrosis, systemic delivery of TGFβ inhibitors or anti-TGFβ antibodies represents a major approach. However, it only decreases the content of active TGFβ. It cannot inhibit TGFβ signaling pathway to prevent myofibroblast formation. Furthermore, the small organic MMP and TGFβ inhibitors have toxicity concerns. The objective of this project is to create drug delivery systems that can be specifically delivered into infarcted hearts to concurrently preserve cardiac ECM, and prevent cardiac fibrosis. Localized delivery will eliminate dose-limiting side effects. The systems will spatiotemporally release MMP-2/9 specific and non-toxic inhibitor, peptide CTTHWGFTLC (CTT), to specifically modulate local MMP-2/9 bioactivity. The systems will also gradually release a multifunctional growth factor bFGF that have anti-fibrotic and proangiogenesis functions. The preserved ECM will thus be vascularized. Vascularization is critical for cardiac ECM as otherwise its structure and composition change over time. In our preliminary work, we have created a fast gelation and degradable hydrogel-based release system capable of efficiently retaining drugs in beating hearts. The system can release CTT for 4 weeks. After being injected into infarcted hearts, the released CTT preserved collagen, increased tissue thickness, and improved cardiac function. Better than many other small organic MMP inhibitors, CTT did not induce cardiac fibrosis. Besides, CTT promoted endothelial cell migration in the presence of TGFβ that is upregulated after MI. These results demonstrate that CTT is potentially a better MMP inhibitor for cardiac therapy than those small organic inhibitors. We have further created a release system that continuously releases both CTT and bFGF. bFGF is known for its angiogenic effect. We found that bFGF is capable of inhibiting TGFβ-induced cardiac fibroblast differentiation into myofibroblast through TGFβ/Erk1/2 pathway. After 4 weeks of implantation, the CTT/bFGF release systems not only increased tissue thickness and preserved collagen composition, but also promoted the formation of a high density of capillaries and remarkably reduced cardiac fibrosis, leading t...